caching: Remember the past to be quicker in the future

In krlmlr/styler: Non-Invasive Pretty Printing of R Code

Remember the past to be quicker in the future

Description

Caching makes styler faster on repeated styling and is shared across all APIs (e.g. style_text() and Addin). That means if you style code that already complies to a style guide and you have previously styled that code, it will be quicker.

Configuring the cache

To comply with the CRAN policy, {styler} will by default clean up cache files that are older than 6 days. This implies that you loose the benefit of the cache for the files not styled in the last 6 days.

If you want to avoid this, i.e., if you want the cache to last longer, you can use the R option styler.cache_root to opt for an indefinitely long-lived cache by setting it to options(styler.cache_root = "styler-perm").

If you are happy with the cache being cleared after 6 days, you can confirm the default and silence this message by setting it instead to options(styler.cache_root = "styler").

You can make this change in your .Rprofile using usethis::edit_r_profile().

Manage the cache

See cache_info(),cache_activate() or cache_clear() for utilities to manage the cache. You can deactivate it altogether with cache_deactivate(). Since we leverage {R.cache} to manage the cache, you can also use any {R.cache} functionality to manipulate it.

In some cases, you want to use a non-standard cache location. In that situation, you can set the path to the cache with the R option R.cache.rootPath or the environment variable R_CACHE_ROOTPATH to an existent path before you call the styler API.

Invalidation

The cache is specific to a version of styler by default, because different versions potentially format code differently. This means after upgrading styler or a style guide you use, the cache will be re-built.

Mechanism and size

The cache works by storing hashed output code as a whole and by expression, which is why it takes zero space on disk (the cache is a directory with empty files which have the hash of output code as name).

The cache literally takes zero space on your disk, only the inode, and you can always manually clean up with cache_clear() or just go to the directory where the cache lives (find it with cache_info()) and manually delete files.

Using a cache for styler in CI/CD

If you want to set up caching in a CI/CD pipeline, we suggest to set the {R.cache} root path to a directory for which you have the cache enabled. This can often be set in config files of CI/CD tools, e.g. see the Travis documentation on caching.

See Also

Other cache managers: cache_activate(), cache_clear(), cache_info()

krlmlr/styler documentation built on Dec. 12, 2024, 8:36 a.m.